Happened at DUB yesterday. The chap in front of me in the Group 1-3 queue was singled out by a Swissport agent before boarding began and told he had to gate check his case (which was well within the size limits) “or you won’t be flying”.

I, immediately behind him and with a similar sized case, was left alone as was - as far as I saw - everyone with a case in the Group 4-9 queue.

The guy complied but was not happy. Like me, he was connecting on to MIA and was told his case would be checked through. I saw him complaining to the cabin crew once on board and taking photos of the overhead bins which weren’t full (it was a Neo with the large bins).